[PATCH] nvme: remove cq check after submission

[Jens Axboe]

On 5/17/18 12:50 AM, Christoph Hellwig wrote:
> On Wed, May 16, 2018 at 03:20:10PM -0600, Keith Busch wrote:
>> On Wed, May 16, 2018 at 01:58:08PM -0600, Jens Axboe wrote:
>>> We always check the completion queue after submitting, but in my testing
>>> this isn't a win even on DRAM/xpoint devices. In some cases it's
>>> actually worse. Kill it.
>>
>> Right, this was on my todo list. Agreed it's not helping anything.
>> Applied to nvme-4.18.
> 
> While I agree in general didn't we have a case where this caused a
> regression last time it came up?  Not that I'd complain if it goes
> away..

Not that I'm aware of. I've been running with this patch for quite
a while, while doing some work on polling.

> But more importantly we could split q_lock into a sq_lock and cq_lock
> now, which might bring real benefits.

Exactly, especially on queue starved setups.

-- 
Jens Axboe